package com.tiancikeji.zaoke.app.common.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * <p>Filter that sets the character encoding to be used in parsing the
 * incoming request, either unconditionally or only if the client did not
 * specify a character encoding. Configuration of this filter is based on
 * the following initialization parameters:</p>
 * <ul>
 * <li><strong>encoding</strong> - The character encoding to be configured
 * for this request, either conditionally or unconditionally based on
 * the <code>ignore</code> initialization parameter. This parameter
 * is required, so there is no default.</li>
 * <li><strong>ignore</strong> - If set to "true", any character encoding
 * specified by the client is ignored, and the value returned by the
 * <code>selectEncoding()</code> method is set. If set to "false,
 * <code>selectEncoding()</code> is called <strong>only</strong> if the
 * client has not already specified an encoding. By default, this
 * parameter is set to "true".</li>
 * </ul>
 *
 * <p>Although this filter can be used unchanged, it is also easy to
 * subclass it and make the <code>selectEncoding()</code> method more
 * intelligent about what encoding to choose, based on characteristics of
 * the incoming request (such as the values of the <code>Accept-Language</code>
 * and <code>User-Agent</code> headers, or a value stashed in the current
 * user's session.</p>
 *
 * @author <a href="mailto:jwtronics@yahoo.com">John Wong</a>
 *
 * @version $Id: SetCharacterEncodingFilter.java,v 1.3 2009/03/02 03:32:20 guyongyong Exp $
 */
public class SetCharacterEncodingFilter implements Filter {

    // ----------------------------------------------------- Instance Variables

    /**
     * The default character encoding to set for requests that pass through
     * this filter.
     */
    protected String encoding = null;

    /**
     * The filter configuration object we are associated with. If this value
     * is null, this filter instance is not currently configured.
     */
    protected FilterConfig filterConfig = null;

    /**
     * Should a character encoding specified by the client be ignored?
     */
    protected boolean ignore = true;

    // --------------------------------------------------------- Public Methods

    /**
     * Take this filter out of service.
     */
    public void destroy() {

        this.encoding = null;
        this.filterConfig = null;

    }

    /**
     * Select and set (if specified) the character encoding to be used to
     * interpret request parameters for this request.
     *
     * @param request The servlet request we are processing
     * @param result The servlet response we are creating
     * @param chain The filter chain we are processing
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet error occurs
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
            ServletException {

        // Conditionally select and set the character encoding to be used
        if (ignore || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null) {
                //        //从HTTP请求的头信息中获取客户端的语言设置
                //      	String clientLanguage = ((HttpServletRequest)request).getHeader("Accept-Language");
                //      	//简体中文浏览器
                //      	if ( clientLanguage.equals("zh-cn") ) {
                //      		request.setCharacterEncoding("GBK"); 
                //      		response.setContentType("text/html; charset=GBK");
                //      		}
                //      	//繁体中文浏览器
                //      	else if ( clientLanguage.equals("zh-tw") ) {
                //      		request.setCharacterEncoding("BIG5");
                //      		response.setContentType("text/html; charset=BIG5");
                //      		}
                //      	//日文浏览器
                //      	else if ( clientLanguage.equals("jp") ) {
                //      		request.setCharacterEncoding("SJIS");
                //      		response.setContentType("text/html; charset=SJIS");
                //      		}
                //      	//缺省认为是英文浏览器
                //      	else {
                //      		request.setCharacterEncoding("ISO-8859-1");
                //      		response.setContentType("text/html; charset=ISO-8859-1");
                //      		}
                request.setCharacterEncoding(encoding);
                response.setContentType("text/html; charset=" + encoding);
            }
        }

        // Pass control on to the next filter
        chain.doFilter(request, response);

    }

    /**
     * Place this filter into service.
     *
     * @param filterConfig The filter configuration object
     */
    public void init(FilterConfig filterConfig) throws ServletException {

        this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("ignore");
        if (value == null) {
            this.ignore = true;
        } else if (value.equalsIgnoreCase("true")) {
            this.ignore = true;
        } else if (value.equalsIgnoreCase("yes")) {
            this.ignore = true;
        } else {
            this.ignore = false;
        }

    }

    // ------------------------------------------------------ Protected Methods

    /**
     * Select an appropriate character encoding to be used, based on the
     * characteristics of the current request and/or filter initialization
     * parameters. If no character encoding should be set, return
     * <code>null</code>.
     * <p>
     * The default implementation unconditionally returns the value configured
     * by the <strong>encoding</strong> initialization parameter for this
     * filter.
     *
     * @param request The servlet request we are processing
     */
    protected String selectEncoding(ServletRequest request) {

        return (this.encoding);

    }

} //EOC
